Features: · Four synchronous buck regulators
· Channel 3: Two-phase, current mode controller
· 4.5V to 18V input range
· Built in sequential startup
· Channels 1 and 2: Independent, 180° out of phase voltage mode controllers
· Single soft start for channels 1 and 2
· Adjustable cycle-by-cycle current limit for each channel
· Adjustable reference current
· Adjustable input under-voltage lockout
· Output over-voltage latch protection
· Output under-voltage protection with delay
· Two comparator inputs for user defined protection - one with delay
· Thermal shutdown
· Self-discharge of output capacitors when the regulator is off
· TSSOP packageApplication· Embedded Computer Systems
· Interactive Games
· Set-top Boxes/Home GatewaysPinout
SpecificationsIf Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Voltages from the indicated pins to SGND/PGND:
VIN, ILIMx, KS3a, KS3b .................................−0.3V to 20V
SWx, RSNSx ......................................−0.3V to (VIN +0.3)V
FB1, FB2, FB3x, VDDx,ON/UVLO...................... −0.3V to 7V
COMPx, FAULT_DELAY, SSx ...........−0.3V to (VLIN5 +0.3)V
CBOOT1 to SW1, CBOOT2 to SW2,
CBOOT3x to SW3x.......................................... −0.3V to 7V
LDRV1, LDRV2, LDRV3x...................... −0.3V to(VDD+0.3)V
HDRV1 to SW1, HDRV2 to SW2,
HDRV3x to SW3x ......................................................−0.3V
HDRV1 to CBOOT1, HDRV2 to
CBOOT2, HDRV3x to CBOOT3x .....................................0.3V
Power Dissipation (TA = 25°C),(Note 2).................... 1.3W
Ambient Storage Temperature.Range.... −65°C to +150°C
Soldering Dwell Time, Temperature(Note 3)
Infrared.....................................................10-20sec, 240°C
Vapor Phase...................................................75sec, 219°C
ESD Rating (Note 4) ........................................................2kV
DescriptionThe LM2648 consists of two current mode and two voltage mode synchronous buck regulator controllers providing 3
outputs at a switching frequency of 300kHz.
Each pair of switching regulator controllers operate 180° out of phase. This feature reduces the input ripple RMS current, thereby significantly reducing the required input capacitance.
The two current mode regulator outputs operate as a dualphase,single output regulator for high current applications.
Current-mode feedback control on Channel 3 assures superior line and load regulation and wide loop bandwidth assures excellent response to fast load transients. Channels 1 and 2 employ voltage-mode feedback control.
The LM2648 features analog soft-start circuitry that is independent of the output load and output capacitance. This
makes the soft-start behavior more predictable than traditional soft-start circuits. Sequential startup is built in and
requires a single capacitor to set the timing.
The LM2648 has over-voltage protection and under-voltage protection for all outputs. Two additional comparator inputs (analog and logic level) are provided to shut down the IC for any user defined protection. The FAULT_DELAY pin allows delayed shut off time for the IC during an under-voltage or PROT-IN2 fault. The LM2648 also features an adjustable UVLO feature.
LM2648 Data Sheet
